James Logan - Tasty genes for mosquitoes

James Logan, LSHTM

Kat - As we head towards the summer, we've got some news that might be useful if you're heading off on vacation to a tropical destination. Holidays can easily be ruined by the misery of mosquito bites, as well as the risk of catching serious diseases such as malaria or dengue fever. But could attractiveness to mossies be in our genes? James Logan, from the London School of Hygiene and Tropical Medicine, has been finding out.

James - So, to test how attractive you are, we use an olfactometer - a Y-shaped tube essentially, which allows us to place volunteers’ hands inside the tube and we test the response of the mosquitoes to odours from volunteers’ hands. So, if mosquitoes are attracted to the hands, they will fly towards them. If they're not attracted, they’ll fly away. So, in our study, we study twins essentially, and we looked at the behaviour of mosquitoes to the orders of identical and non-identical twins.

Kat - Because identical twins should have pretty much matching genes whereas non-identical twins are as alike as brother and sister.

James - That’s exactly right, yeah. So, the idea is that if there is some sort of genetic control going on, we’d be able to see that in the behaviour of the mosquitoes. So, the hypothesis was that identical twins would be similar in their level of attractiveness and non-identical twins would be different.

Kat - I'm a bit concerned that you're getting volunteers to shove their hands in a tube full of mosquitoes. Are they going to get bitten?

James - Well, in this particular experiment, the volunteers don’t get bitten. There is a mesh between the mosquitoes and their hands so they don’t actually get bitten. But I have to say, we do other experiments where people get do bitten and they're pretty happy to do it.

Kat - It sounds crazy, but regardless of whether they did or didn’t get bitten, what did you find when you wafted these mosquitoes towards the different people’s hands?

James - In our test we looked at about 40 sets of twins. What we found in our experiment was that mosquitoes were equally attracted to odours from identical twins. When we subjected them to odours from non-identical twins, that correlation wasn’t there. so, what that told us was that identical twins were similar in their level of attractiveness to mosquitoes which suggests that there is some sort of genetic control of how attractive you are to mosquitoes.

Kat - We hear a lot in the media about genes controlling things like our height, our IQ, our risk of diseases. How does this sort of level of attractiveness to mossies compare?

James - When we do this experiment, we have to do a calculation for heritability and that gives us a value between nought and one. The values that we got were quite high, astonishingly high actually, quite surprising. Really at the sort of level of the same sort of values you would get for IQ and height. So, it really was quite surprising. It seems to be very strong sort of genetic component.

Kat - We also know things like high IQ, they're not necessarily just one gene. Is it that there's a gene for attractiveness to mosquitoes and some people have one version or another, or is it going to be more complicated than that?

James - At this stage, we don’t know. So, we know that there's something going on genetically. The next stage of the study is then to identify the genes involved. There could be more than one gene that probably is more than one gene involved. We know that mosquitoes respond to odours and how attractive you are is determined by the odours that you produce. These odours can be produced in different ways. They might be produced by the body itself. It might be produced via the skin bacteria which can also be influenced by your genetics. So, there's a lot of unanswered questions here, but it’s really exciting, now that we can go on to the next stage and look at the genes.

Kat - So, once you do find these gene or genes that might be involved, what's the plan? Is it just to be able to test someone go bad luck, maybe don’t go on holiday somewhere where there's mosquitoes?

James - I mean, that is something that we could think about. I mean, you can have your genome screened for all sorts of things nowadays and that could be one of the things that we look at, your susceptibility to being bitten by mosquitoes. That has more serious implications for populations in disease-endemic countries where malaria or dengue is a problem for example. So, we could look at the risk of certain populations and take into account how likely they are to be bitten when we do predictive modelling. But more than that, we could possibly develop a new technology. So, you might imagine taking a pill when you go on a holiday which causes the body to naturally upregulate the production of these natural repellents which is what make us unattractive and that would minimise the need for putting topical repellents on the skin.

Kat - There's a lot of sort of folklore and old wives’ tales about maybe you should eat garlic or drink different things to repel mosquitoes. Is there any truth in that, now we’re getting towards the summer holiday season?

James - It would be good if there was. A lot of people have various anecdotes about Guinness, is one of them, or gin, garlic, vitamin B. the truth is, there is no evidence that it can make you less attracted to mosquitoes. In fact, studies have been done which have shown that vitamin B for example has no effect on how attractive you are to mosquitoes. One study in 2010 showed that if you drank beer, it made you more attractive. So, take that advice as you will. I'm not sure whether that stops people drinking beer when they go on a holiday, but the difference wasn’t very big, so I wouldn’t be too worried about it.

Kat - I’m happy to risk it… James Logan there from the London School of Hygiene and Tropical Medicine.

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